Artificial joints, such as an artificial hip, are often attached to a structurally sound bone by a stem lodged in a cavity formed in the bone. To create the cavity, a surgeon may remove worn or diseased bone structure and then drill and hollow out a cavity along the medullary canal of the bone. The cavity is ultimately shaped to accommodate the stem of the prosthesis. The prosthesis is secured in place by a combination of cement, pressure between the bone and the prosthesis, or mechanical structure such as screws or pins. If the cavity conforms to the shape of the stem, a better implant can be expected.
To create the cavity, a surgeon may use a shaped broach which conforms to the shape of the prosthesis stem. In the past, the broach has been mounted on a handle and hammered into the bone. This is an arduous procedure, which relies greatly on the skill and strength of the surgeon. Some variation in the strength and direction of the applied blows is inevitable, and this results in variation in size and placement of the cavity. Moreover, the force required for the operation, coupled with a wedge-shaped broach, will sometimes split the bone.
To overcome some of these disadvantages, power rasps have been proposed, such as one produced by Allo Pro. The Allo Pro power rasp is pneumatically driven with a trigger-operated hand control and a switched valve for forward and reverse operation. We believe, however, that there is still a need for a pneumatically powered orthopedic broach with ergonometric control.